1. Field of the Invention
The present invention relates to stabilized gimbal platforms and in particular relates to stabilized gimbal platforms suitable for missile seekers which have two axis gimbal rings mounted within a bail gimbal.
2. Description of the Prior Art
Rate gyro stabilized platforms have been used for several decades. The customary design for such a rate gyro stabilized platform consists of a gimbal ring interface with pitch and yaw rotational freedom between the moving platform and the fixed body. Given a platform size the body diameter reduces the gimbal angles possible as the body diameter decreases. To provide three dimensional stability, or larger gimbal angles, a conventional approach calls for the addition of a roll axis behind the yaw and pitch axes. An alternate approach to achieving large gimbal angles in a small body diameter is to support one platform axis on a bail gimbal with off-axis bearings for support and an off-axis torque motor drive. However, the off-axis bail gimbal presents high friction of the bail gimbal which restricts precise stabilization.
The restriction of bail gimbals for precise stabilization has become magnified in current missile bodies which seek to perform at higher turning accelerations. A small body diameter is desirable. Small bodies have less aerodynamic friction and permit a larger number of missiles to be carried by a launch platform such as an aircraft. Further, although a two-axis bail gimbal allows packaging a large stabilized platform with large gimbal angles in a small missile body diameter, the stabilization is poor due to high friction.